Allen has won three straight since back-to-back losses to Nassourdine Imavov and Anthony Hernandez. He beat Marvin Vettori, Reinier de Ridder and Edmen Shahbazyan in that run.
Duncan has won five in a row. His latest, a July decision over iron-tough veteran Jared Cannonier, was probably the best win of his UFC run. He owns an 8-2 record in the promotion.
The winner stays in the hunt for a future title shot in a deep division. Allen ranks higher, yet he sits in a sort of limbo, and facing the lower-ranked Duncan shows it.
Prelims start at 5 p.m. ET, and the main card follows at 8 p.m. ET on Paramount+. The service includes UFC Fight Night with a subscription at no extra fee, with plans starting at $8.99 a month or $89.99 a year. Paramount+ streams all 13 UFC numbered events and 30 Fight Nights exclusively, and the deal runs seven years through 2033.